1. Field of the Invention
The present invention relates to a manufacturing method for a display device using an organic electroluminescence element (organic EL element) and to a display device manufactured thereby.
2. Description of the Related Art
In recent years, flat panel display device including liquid crystal element, organic EL element or the like are widely used. FIG. 7 schematically shows the structure of an organic EL element 1. An anode 3, an organic EL layer 8 including a hole transporting layer 4, a light-emitting layer 5, and an electron transporting layer 6, a cathode 7, and others are formed on a substrate 2 made of, for example, glass. Upon application of an electric field to the electrodes 3 and 7 through a lead 9, the region of the light-emitting layer 5 sandwiched between the electrodes 3 and 7 is excited to emit light.
Generally, when displaying color, it is necessary to array plural pixels that include sub-pixels with different light-emitting colors to each other, such as red (R), green (G) and blue (B), on a substrate in two perpendicular directions, for example in columns and rows.
In order to manufacture a display device for color display using an organic EL element, for example, an anode in a stripe pattern may be formed on a substrate, and then organic coloring materials may be vapor deposited in sequence on the anode to form organic EL layers corresponding to RGB, the organic EL layers being exposed in a repeating pattern. A cathode may then be formed on the organic EL layers, such that adjacent RGB organic EL layer portions that have been sandwiched between the electrodes each form sub-pixels, these sub-pixels together configuring single pixels. Multiple of these pixels that include the RGB sub-pixels are thereby arrayed in two directions, columns and rows, on a substrate.
Regarding such a substrate, display devices have been proposed that use, instead of a glass substrate, a flexible substrate, such as a resin film or metal plate (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 7-78690, JP-A No. 2002-15859, and JP-A No. 2004-361774). By the use of a flexible substrate that does not crack even when bent by a large degree, a display device with high impact resistance may be provided. In particular flexible substrates formed from a resin film have the merits of high transmittance and light weight.
During the manufacture of a display device using a flexible substrate formed from a resin film, in particular, in the process before film forming of the organic EL layers, if the amount of dimensional change of the substrate differs when forming, for example, the electrodes (anode), insulating layer, dividers and the like, then when the organic light-emitting layers corresponding to RGB are formed as films, the positions of the sub-pixels may be misaligned to a great extent from the design positions thereof.
FIG. 8 schematically shows misalignment of electrodes, which form the sub-pixels of organic light-emitting layers that correspond to RGB within the pixels, from the design position of the electrodes. When the initial substrate 60 expands in the processes before film forming of the organic EL layers, with a large amount of dimensional change, then portions of electrodes 72 on a substrate 70 are greatly misaligned from the design positions 62. If the position of the electrodes 72 on the substrate 70 are greatly misaligned from the design positions 62 then, as shown in FIG. 9, when forming the light-emitting layers that form the sub-pixels with mask vapor deposition using a shadow mask 80, the margin for separate patterning process by vapor deposition is decreased, and separate patterning process by vapor deposition may not be possible in some cases. It should be noted that this type of problem is not limited to separate patterning process by mask vapor deposition; for example, when coating separation is carried out by a transfer method, if the electrodes are greatly misaligned from their design positions, then problems occur with reduced margin for separate patterning process or separate patterning process becomes impossible.